The present invention generally relates to rollover sensors and, more particularly, to vehicle rollover detection which anticipates vehicle dynamics for sensing a rollover condition of a vehicle.
Increasingly, automotive vehicles are employing safety-related devices that deploy in the event that the vehicle experiences a rollover so as to provide added protection to the occupants of the vehicle. For example, upon detecting a vehicle rollover condition, a pop-up roll bar can be deployed such that, when activated, the roll bar further extends vertically outward to increase the height of support provided by the roll bar during a rollover event. Other controllable features may include deployment of one or more air bags, such as frontal air bags, side mounted air bags, and roof rail air bags, or actuating a pretensioner to pretension a restraining device, such as a seatbelt or safety harness, to prevent occupants of the vehicle from ejecting from the vehicle or colliding with the roof of the vehicle during a rollover event.
In the past, mechanical-based rollover sensors have been employed in automotive vehicles to measure the angular position of the vehicle from which a rollover condition can be determined. The mechanical sensors have included the use of a pendulum normally suspended vertically downward due to the Earth""s gravitational force. Many mechanical automotive sensing devices are employed simply to monitor the angular position of the vehicle relative to a horizontal level ground position. As a consequence, such mechanical automotive sensors have generally been susceptible to error when the vehicle travels around a corner or becomes airborne, in which case the Earth""s gravitational force, which the sensor relies upon, may be overcome by other forces.
More sophisticated rollover sensing approaches require the use of as many as six sensors including three accelerometers and three angular rate sensors, also referred to as gyros, and a microprocessor for processing the sensed signals. The three accelerometers generally provide lateral, longitudinal, and vertical acceleration measurements of the vehicle, while the three gyros measure angular pitch rate, roll rate, and yaw rate. However, such sophisticated rollover sensing approaches generally require a large number of sensors which add to the cost and complexity of the overall system. In addition, known sophisticated systems are generally susceptible to cumulative drift errors, and therefore occasionally must be reset.
In an attempt to minimize the number of sensors required, conventional sensing approaches have employed, at a minimum, both an angular rate sensor and an accelerometer. For those sensors designed to detect both rollover and pitchover events, a second angular rate sensor and a second accelerometer are typically added. While the angular rate sensor can be integrated to calculate a roll angle, in practice, angular rate sensors typically generate a non-zero, time-varying output, even in the absence of a roll rate. This bias may cause a significant error in the integration-generated roll angle, and such bias must be compensated in order to provide an accurate sensed measurement. Accordingly, conventional rollover sensing approaches typically require auxiliary sensors, in lieu of the single angular rate sensor, to compensate for zero-input biases inherent in many angular rate sensors.
While prior known rollover sensors have been developed to detect rollover events, it is possible that certain rollover events may be difficult to detect well in advance. For example, when a vehicle loses positive traction with the road surface and begins to yaw and slide sideways in a lateral direction, the vehicle becomes increasingly susceptible to rollover upon engaging a tripping mechanism, such as a curb or a high-friction surface such as soft soil or gravel, or undergoing a fall over event, such as sliding off a highway embankment. Such lateral vehicle motion may occur when the vehicle travels on a low friction roadway, such as may occur in slick weather conditions with rain, snow, or ice. When such events occur that lead to lateral vehicle motion, it is desirable to achieve timely deployment of appropriate restraint devices.
Accordingly, it is desirable to provide for an accurate and timely rollover detection apparatus and method that detects a vehicle rollover event during various driving conditions. More particularly, it is desirable to provide for a rollover detection apparatus and method that detects an upcoming rollover event when the vehicle is subjected to a lateral sliding movement, such as when the vehicle loses positive traction with the road surface, and engages a tripping mechanism.
In accordance with the teachings of the present invention, a vehicle rollover sensing apparatus and method are provided for detecting an anticipated rollover event for a vehicle, and thus allowing for timely deployment of safety-related devices. The rollover sensing apparatus includes a rollover sensor for sensing a roll-related event of a vehicle and producing a rollover signal. The rollover detection apparatus also includes a lateral sensor for sensing lateral dynamics of the vehicle and producing a lateral dynamics signal indicative thereof. A controller determines an anticipated rollover event of the vehicle as a function of the rollover signal and a rollover detection sensitivity, and further adjusts the rollover detection sensitivity as a function of the lateral dynamics signal.
A method is also provided for detecting an anticipated rollover event for a vehicle. The method includes the steps of sensing a rollover related event for the vehicle and producing a first signal indicative thereof. The method also includes the steps of sensing lateral dynamics of the vehicle and producing a second signal indicative thereof, and determining an anticipated rollover event of the vehicle as a function of the first signal and a sensitivity of the rollover detection. The method further includes the step of adjusting the sensitivity of the rollover detection based on the second sensed signal and providing an updated vehicle rollover event based on the adjusted sensitivity.
Accordingly, the rollover sensing apparatus and method of the present invention advantageously anticipates vehicle dynamics prior to a rollover event to detect a rollover event of a vehicle. It should be appreciated that the rollover detection apparatus and method of the present invention achieves timely deployment of a rollover signal which allows for the appropriate restraint systems to be deployed in the event where a lateral sliding motion precedes a rollover event.